Strength degradation and anchoring behavior of rock mass in the fault fracture zone

Rock mass in the fault fracture zone has some characteristics such as low strength and poor self-stability, so the control mechanism of stability has been a difficulty in the research of underground engineering. A set of laboratory simulation method of fault fractured rock mass is developed to reflect the natural forming process of fault fracture zone. Compared with intact rock mass, the fault fractured rock mass has an obvious degradation in strength and deformation parameters, and the degradation index is between 22.79 and 84.06%. The bolt has a certain supporting effect on the fault fractured rock mass, and in the situation of end anchoring, the greater the pretightening force is, the better the enforcement effect will be. The stress field produced by high pretightening force can relieve the stress concentration around the bolt hole and make the initial cracks of rock mass away from the bolt plate. The evolution curve of bolt axial force in the process of uniaxial compression of large-scale specimen shows four stages, which are the initial compression stage, pre-peak joint load-bearing stage, post-peak joint load-bearing stage and the residual stage. Research results could provide some theory reference for the stability control of rock mass in the fault fracture zone.     

黔西南地区煤系地层井壁稳定技术探讨

井壁稳定性问题对黔西南地区煤系气的勘探开发效果至关重要。对泥页岩和煤岩井壁失稳的机理进行了分析,从化学、力学和化学与力学耦合等方面,探讨了煤泥互层段井壁失稳的对策。结合黔西南地区煤系地层煤层气井的实例,分析了井壁失稳对井径大小及岩心采取率的影响,发现煤泥互层段的井径扩大率较大而相应的岩心采取率较小。尽可能准确地预测探井的地层压力、选用合理的钻井液体系和密度、采用合理的钻井工艺有助于维持黔西南地区煤系地层井壁稳定。     

温压耦合影响下科学钻探深井结晶岩层井壁稳定性分析

科学钻探深井结晶岩处在高地应力、高地层压力和高地温的“三高”环境中,自身的结构特征和物化特性会发生根本性变化,因温度变化引起的应力变化极易导致井壁失稳。本文依据温压耦合影响下坍塌压力和破裂压力计算模式,确定不同井壁温度下的安全钻井液密度窗口,通过FLAC3D开展温压耦合影响下井壁稳定数值模拟,分析在不同钻井液密度下井眼打开后不同时间的井壁周边温度和井壁稳定变化情况。结果表明：地层弹性参数对地层破裂压力的影响较大,对于花岗岩此类弹性模量较大的结晶岩,温度变化对破裂压力影响更大;井壁处附加应力受温度变化的影响程度：附加周向应力>附加径向应力>附加垂向应力;在最小主应力方向的井壁周边地层等效应力与钻井液密度呈正比关系,在最大主应力方向呈反比关系。     

考虑围岩应变软化及采空区接触的深部煤层底板破坏分析

为研究深部煤层开采底板破坏形态,提出考虑围岩应变软化和采空区接触的FLAC3D有限差分数值方法,以河北开平煤田林西矿2023工作面底板实测导水裂隙带为工程背景,结合朗肯土压力理论定性分析,研究深部煤层底板破坏特征。结果表明:采用应变软化本构关系代替常用摩尔–库伦本构关系能够对围岩塑性破坏后的力学状态更准确表述;采用“应变软化–空–弹性”模型转变的方法,达到模拟采空区顶板垮落后应力传递的效果,弥补了以往煤层开采模拟中采空区垮落后顶底板不接触的固有缺陷;通过采空区顶底板接触与否条件下应力、位移的对比,发现采空区是否接触对数值结果影响巨大,突出考虑采空区接触的必要性;根据模拟结果中塑性剪切应变率的变化,实现了底板滑移面的三维显示,形态为斜向采空区的半包围面状结构;结合朗肯土压力理论将底板塑性区与主动区、过渡区和被动区对应,3个区破坏形式分别为剪切破坏、剪切破坏、拉张与剪切的交互破坏。提出的考虑围岩应变软化及采空区接触的FLAC3D数值方法对煤层开采模拟实现了优化,并可为其他大变形后需考虑接触的工程模拟提供参考。      

韧性剪切带内的流体与岩石相互作用研究进展

构造变形与流体联合控制成矿作用的机制是矿床学界关注的热点问题之一。作为大陆岩石圈中的应变局部化带,剪切带中一般都渗透着大量流体,流体与岩石的相互作用及其化学效应和物理效应,导致了矿物化学不平衡和组分的迁移,引起岩石化学成分重新调整。文章通过对韧性剪切带内的流体作用、剪切带内的成分与体积变化、剪切变形与成矿模拟实验总结,讨论了剪切变形过程中的力学-化学作用、剪切构造应力和流体在构造成岩成矿过程中的行为。因此,要加强构造应力对温度、岩石物理性质、地球化学相平衡和水岩体系的相关参量方面影响的综合研究。     

水泥浆液在岩体裂隙中的流动沉积机理

研究了水泥颗粒开始沉积时浆液最小流动速度(临界速度)、裂隙中水泥颗粒沉积分布规律与排水方式等,提出了临界速度值以及浆液流动通道形成的起点至注浆孔的距离的计算公式,进一步揭示了水泥浆液在岩体裂隙中的流动沉积机理。     

Probabilistic analysis of crushed zone for rock blasting

Transmission of explosion waves through a rock medium causes a severe vibration that stimulates the mechanical behavior of rock mass. This stimulation imposes highly concentrated stresses on the ends of existing fine joints and depending on the toughness of the rock, causes them to propagate rapidly. Consequently, the propagation and joining of cracks form a crushed zone around the blast hole. Several studies are available in the literature to estimate the radius of crushed zone, deterministically. In this paper, however, a probabilistic approach has been adopted. This is because the initiation and propagation of cracks have a probabilistic nature, and neither the initial state of the rock nor the explosion load could be expressed in a fully deterministic way. Thus, after generating random values for involved parameters, including explosive density, detonation velocity, dynamic Young’s modulus, dynamic Poisson’s ratio, uniaxial compressive strength, and borehole radius, the Monte-Carlo sampling method was adopted to calculate the exceeding probability of the crushed zone radius from desired values. The results showed that the exceedance probability for the growth of cracks falls sharply by the increase in the crushed zone radius so that the probability of crushed zone radius longer than 0.5 m is less than one percent. The results of this study, compared to the deterministic models, provide advantages in that they are not only limited to a certain value for the crushed zone radius and show the probability of exceedance for any desired radius.     

Evolution of sedimentary rock formation of a rock association level

The evolution of sedimentary rock formation of a highly organized level (paragenetic rock associations) is more complex than that of a poorly organized level (rocks). Subjacent rock associations are established for the entire geological evolution of the Earth: they varied in time and were obsolescent or, in contrast, nascent and momentary. A certain cyclicity of evolution is identified along with directed changes.     

A water zone propagating through a permeable rock

SummaryA Water Zone Propagating Through a Permeable Rock A one-dimensional front of a water zone penetrating an initially dry permeable medium is studied theoretically as well as experimentally. The theory includes the case when the permeability varies with position. Simple experiment and theory show that the front of the water zone increases as the square root of time if the permeability is constant. A method is suggested to measure the non-constant permeability by measuring the penetration rate.

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ZusammenfassungAusbreitung einer Wasserzone im durchlässigen Fels Eine Front von einer Wasserzone, die durch ein permeables eindimensionales Medium dringt, ist genau beobachtet worden, sowohl theoretisch als auch experimentell. Die Theorie beinhaltet den Fall, daß die Permeabilität nicht konstant ist, sondern mit der Lagekoordinate wechselt. Einfache Experimente und Theorien beweisen, daß die Lage der Front der Wasserzone mit der Quadratwurzel der Zeit erweitert wird, wenn die Permeabilität konstant ist. Eine Methode wird vorgeschlagen, wie man die variable Permeabilität durch das Messen der Eindringungsgeschwindigkeit mißt.

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RésuméExtension d'une zone d'eau dans une roche perméable Un front d'une zone d'eau, pénétrant un milieu perméable et à une dimension, a été étudié non seulement théoriquement mais encore expérimentalement. La théorie comprend le cas où la perméabilité n'est pas constante mais met de la variété avec les coordonnées. De simples expériences et des théories donnent que la position du front de la zone d'eau augmente comme la racine du temps si la perméabilité est constante. Un procédé proposé est que l'on mesure la perméabilité d'un variable à force de mesurer la vitesse de la pénétration.

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Nomenclature g gravity acceleration m/s² - k reciprocal reference length m^–1 - L length of rock specimen m - p pressure Pa - p0 reference pressure Pa - R position of the front of the water zone m - t time s - u velocity of water m/s - x position coordinate m - permeability m² - ₀ reference permeability m² - viscosity of water Ns/m² - integration variable m - density of water kg/m³ With 6 Figures     

包气带中原油的迁移和降解研究

在石油的开采和集输过程中,常常有大量的原油抛洒和泄漏,这对土壤和植物地造成严重污染,本文通过大量野外和室内的原油渗透试验,含油地层的淋滤试验和石油的生物降解试验,来研究石油污染物在包气带中迁移,转化和降解规律,从而地下水石油污染的潜在性作出科学的评价。     

A constitutive model for a laboratory rock joint with multi-scale asperity degradation

This paper presents a joint constitutive model that considers separately the mechanical contribution of waviness and unevenness of a joint to shear behaviour. The critical asperities for waviness and unevenness are determined from geometric properties in a lab-scale joint. The wear process is employed to model the degradation in dilation and strength during shear. From dimensional analysis, asperity degradation constants are developed using geometric parameters including asperity angle, wavelength, and amplitude as well as rock strength and stress. The applicability of the proposed model was assessed by performing direct shear tests on three joint roughness coefficient (JRC) profiles and providing its correlation with experimental results. Additionally, experimental data taken from literature were used to validate the model’s performance.     

含层间错动带岩体的破坏模式及其剪切特性研究方法探讨

层间错动带存在的普遍性,给世界上许多工程带来了岩体稳定性问题和地质灾害。通过对因层间错动带导致工程岩体结构变形失效或破坏的实例进行归纳总结,采用岩体结构控制理论的观点将含层间错动带的岩体的破坏模式分为拉裂破坏、掉块和层间剪切滑移破坏3大类。以此为基础,提出剪切力学模型是层间错动带力学模型研究的重点。对层间错动带剪切力学特性的现有试验方法和建模理论进行评述,并根据现有的研究基础,提出屈服面蠕变模型是当前层间错动带剪切蠕变模型的较好选择。     

Remanent magnetism anisotropy and rock formation

Conditions of rock formation most favorable for the emergence of high anisotropy are present within the zones of folding, considerable compression, deep-seated and contact metamorphism, and marginal zones of the intrusions; to a smaller extent they exist in tuffs and ignimbrites.--IGR Staff     

Water effects on rock strength and stiffness degradation

Reduction in strength and stiffness in rocks attributed to an increase in water content has been extensively researched on a large variety of rock types over the past decades. Due to the considerable variations of texture and lithology, the extent of water-weakening effect is highly varied among different rock types, spanning from nearly negligible in quartzite to 90 % of uniaxial compressive strength reduction in shale. Readers, however, often face difficulties in comparing the data published in different sources due to the discrepancy of experimental procedures of obtaining the water saturation state and how the raw laboratory data is interpreted. In view of this, the present paper first reviews the terminologies commonly used to quantify the amount of water stored in rocks. The second part of the paper reviews the water-weakening effects on rock strengths, particularly focusing on uniaxial compressive strength and modulus, as well as tensile strength, under quasi-static loading and dynamic loading. The correlation relationships established among various parameters, including porosity, density and fabric of rocks, and external factors such as strain rate, surface tension and dielectric constant of the saturating liquid, absorption percentage and suction pressure, are reviewed and presented toward the end of the paper.     

川藏铁路复杂地层水平孔钻探护壁堵漏研究与应用

川藏铁路地处青藏高原东南部,由于构造活动发育,岩体松散破碎,裂隙及承压水发育,勘察这些地层过程中时常发生塌孔、掉块卡钻、冲洗液漏失等复杂情况。本文针对隧道出口段地层设计的定向水平孔,在钻进过程中出现孔壁失稳和冲洗液漏失等问题,通过分析孔内地层特征、漏失情况,提出了适宜的冲洗液体系。随后,进行正交实验快速得到护壁堵漏材料掺量的最优组合,并通过后续的工程实践结果验证并改进,使得冲洗液工艺效果明显。优化配方后的冲洗液,能够大幅度减少孔内事故,有效地促进勘探进度,取得了显著的经济效益和社会效益。     

Modeling hydraulic fracture propagation using cohesive zone model equipped with frictional contact capability

We present a new pore pressure cohesive element for modeling the propagation of hydraulically induced fracture. The Park-Paulino-Roesler cohesive zone model has been employed to characterize the fracturing behavior. Coulomb’s frictional contact model has been incorporated into the element to model the possible shear reactivation of pre-existing natural fractures. The developed element has been validated through a series of single-element tests and an available analytical solution. Furthermore, intersection behaviors between the hydraulic fracture and the natural fracture under various conditions have been predicted using the present element, which shows good agreement with experimental results.